A Reason to be Evil
by xxApocalypsexx
Summary: Frisk finds himself once again fighting against a familiar face. But why would he return a second time? ONESHOT


**A Reason to be Evil**

 **A/N: I found out about this charming little game, and decided to watch some breakthroughs of it(being broke sucks). Watching a Genocide run had this little plot bunny pop into my head. Also, just for clarification, this story takes place in a Genocide Run that happened after another Genocide Run. Enjoy.**

* * *

Again, the battle raged on. Every time **IT** attempted to attack, Sans would dodge, something that no other monster apparently thought of.

 _'It can't go on like this...I'll mess up eventually'_ Sans thought to himself.

The timelines Sans had observed, he knew how it would end. Everything would disappear, and the only thing left that could avert that...was him. The lazy skeleton with a penchant for bad puns...Sans.

 _'What a joke. I'm so tired...but I can't be lazy now. Now, of all times, I have to be strong, and I can't just sit back and do nothing. I have to make sure...their deaths weren't in vain!'_

Sans gave his warning, knowing **IT** had heard it all before, and would not listen. Just one more turn...and Sans would unlease his 'Special Attack', and trap **IT** forever...or until it reset everything once again.

In all honesty, there were four possibilities right now.

Sans could win, and kill **IT** , and the timeline immediately ends, **IT** using its power to escape to another timeline.

Sans could lose, and everything is destroyed in an instant.

Sans could use his _'Special Attack'_ , to trap **IT** forever in an endless battle with no escape. Of course, **IT's** power allows it to even escape that.

And the last... **IT** spares Sans, against all reason. But the fifth timeline, the one Sans refused to allow...it was the reason Sans chose the brutality of the fourth...where Sans crushes **IT** to death after **IT** stops fighting.

 _'No matter what, I won't be the one who condemns humanity, as well as the King. I'll die before I let that happen.'_

Another attack, and Sans dodges again.

 _'My only hope is to hold **IT** off for so long that it gets frustrated and gives up...Heh...like **IT** will ever give up.'_

"Well, here goes nothing. Survive **THIS** , and I'll show you my special attack."

Sans throws everything he has at **IT** , trying to finish **IT** off, and knowing **IT** knows his moves before he makes them...an impossible foe.

 **IT** dodges with perfect evasion, a precision born of endless repetition, and Sans let his frustration and anger towards **IT** for killing his friends and his brother go wild for a moment, slamming **IT** into the walls, into the ceiling, the floor, anything at all. Sans manages to severly hurt **IT**...but can't finish **IT** like this. Slowly, Sans runs out of energy and **IT** comes to a stop, with but a single HP remaining.

"Yep, that's right, it's..." Sans began to speak, but was interrupted.

"Literally nothing. And it won't ever be anything...right Sans?" **IT** spoke for the first time, pushing itself off the floor.

"About time you said something. Was getting a little too quiet, with just me talking. But why now? What could you possibly say that would make a difference at this point." Sans said.

"...I know you hate me. You can't understand my motivations, you've seen me kill or cause the death of everyone you know and love. Your brother, Papyrus. The heroine, Undyne. The shy scientist, Alphys. Even Mettaton, that possessed hunk of metal that is pretty much the only entertainment you have down here. You can't understand why I would kill them, can you?"

Sans was stunned. He hadn't seen this coming, despite all of his knowledge about the various timelines. Despite this, he refused to drop his guard. It could just be a trick.

"I can clear it up for you...let me tell you a story. It's about a human who fell into a world filled with monsters. He embarked on a journey, befriended everything and everyone, and managed to create a perfect, peaceful future. But it didn't end there. One day, the human found himself back at the beginning again, and his only proof that anything had happened at all...was a damn flower that would kill you with no remorse. The human tried everything he could think of to escape. Fighting...not fighting, begging to be released, and yet unable to let go of life. Even when he was pushed to the brink of oblivion, he would muster his Determination, and LOAD."

 _'That's what he calls his ability...the way he shifts the timelines.'_

"Yeah, thats why the timelines are so crazy. In the end, the human chose a horrible path. He chose to murder everything and everyone in the underground. He chose Genocide. The last chance he had to escape. And it worked...but it had a terrible cost.

He learned that another person was guiding his actions. The human named Frisk...overshadowed by another...Chara, the adoptive child of Asgore...the first human to enter the Underground. Her hatred of both humanity and monsters transcended her own death, and found a resting place in Frisk. She was what drove him to fight and kill, to gain as much power as he could, when his own will to continue flagged. And in the end, she destroyed the world. The end of everything you so fear." Frisk said.

"But then...how are you here?" Sans found himself intrigued by Frisk's story. If they were going to be trapped her forever, may as well have some free entertainment. Frisk closed his eyes, and sighed, before continuing his story, no longer bothering to mask the fact that he was talking about himself."

"I floated in a void for what seemed like forever. Then **SHE** appeared again. She offered to restore the world, in exchange for one thing."

"What was that?" Sans asked, genuinely curious.

"My SOUL. I knew I would regret it, but I couldn't let my friends be lost completely to that limbo. Now, I'm locked here in a different way. Should I choose to recreate that shining future, the one I had long ago... **SHE** would be there, ready to unleash destruction on the whole world. She would use the opportunity to destroy all the friends I'd ever made, in ways that make my rampage look like a friendly game."

"So what will you do?" Sans found himself asking.

"The only thing I can. I will remain here forever. You trapped me in a way that I can't attack, not without significant effort. I can resist **HER** that much. But the only way to reach this point...was to recreate that hated Timeline...the 'Genocide' Timeline. Everyone may have died...but they died facing a great evil, not stabbed in the back by someone why trusted. Of the two options I had, I chose the less painful one. At least they never knew I was their friend. But I knew, you were different. You always seemed to know when I reset. Hell, our battle is proof of that."

"...I don't entirely believe you. You could just be trying to get me to lower my guard."

"Yeah, I figured you wouldn't trust me, at least not fully, and that's a good thing, seeing as Chara's influence on me is still very strong. After all, I'm covered in the remains of all the other monsters, and a single touch is all it would take to destroy you, at my current **LV**. Just keep in mind...if I lose the battle with Chara, she'll push this box and attack you, and keep doing it until she hits you. Don't ever let your guard down."

"If I kill you, then that's it. Her influence over me will be total. I have 19 **LV** at the moment, and 20 is the threshold where I completely lose control. Even though **SHE** holds my SOUL, **SHE** can't act until I kill Asgore and Flowey."

He turned, a tear dropping from his eye.

"Sans...my first friend...I trust you to be my jailer. Make sure I can't hurt anyone else. And please...don't die."

With those words, Frisk lay down, and fell into a light sleep. Almost instantly, he seemed to be engulfed by nightmares. Unfortunately, there was little Sans could do, and if he were being honest with himself, he hadn't fully forgiven the young human for his misdeeds.

It was strange, looking at this young human, coated in the ashen dust of my fellow monsters, and watching him give up on ever doing anything productive again, and yet still having that spark, that Determination, that wouldn't let him just lie down and die. Sans knew if he struck down Frisk at this moment, Frisk would reset, unable to help himself. Their battle would begin anew.

Sans closed his eyes, weariness evident in the way he stood.

 _'How strange...A new timeline has appeared. One that didn't exist before.'_

A young human, who slowly succumbs to age and perishes, dragging his SOUL to wherever human souls go...and carrying a great darkness with him. But there are many offshoots where Sans is caught off guard, and Chara destroys the world, pushing Frisk ever closer to insanity as he is forced to re-kill his friends once again.

"Heh, I won't let her _get under my skin_. Even if I hate you...I'll fulfill your final wish Frisk...my once upon a time friend."


End file.
